Contact lenses have been popularized remarkably in recent years, and not only hard contact lenses and soft contact lenses but also disposable contact lenses are widely used. These contact lenses are classified into ionic and nonionic contact lenses, and materials of the ionic contact lenses to be used are polymers (or copolymers) obtained by polymerizing (or copolymerizing) hydroxyethyl methacrylate, methyl methacrylate, methacrylic acid and the like.
Since a lacrimal fluid layer existing on a front face of contact lenses in wearing and a lacrimal fluid layer existing between a rear face of the contact lenses and the surface of eyeballs are very thin and unstable, a lacrimal fluid on the surface of the eyeballs of the wearers disappears faster than those of persons who do not wear contact lenses. As a result, the lacrimal fluid on the surface of the eyeballs often becomes deficient at short intervals when the wearers blink, and feel in wearing the contact lenses deteriorates, i.e. dryness and unpleasantness in eyes occur. Further, chronic deficiency of the lacrimal fluid on the surface of the eyeballs of the wearers is responsible for serious disorders in external eye segment such as conjunctiva and cornea.
The very thin lacrimal fluid layers existing on the front and rear faces of the contact lenses in wearing work as cushions on the eyeballs and eyelids of the wearers. Accordingly, a system to maintain the lacrimal fluid layer on the surface of the eyeballs of the wearers in a stable state is required in order to improve the wearing feel and prevent the disorders from occurring in the external eye segment such as conjunctiva and cornea.